Ocean Alkalinity System And Method For Capturing Atmospheric Carbon Dioxide

ABSTRACT

An ocean alkalinity enhancement (OAE) system that reduces atmospheric CO2 and mitigates ocean acidification by electrochemically processing feedstock solution (e.g., seawater or brine) to generate an alkalinity product that is then supplied to the ocean. The OAE system includes a base-generating device and a control circuit disposed within a modular system housing deployed near a salt feedstock. The base-generating device (e.g., a bipolar electrodialysis (BPED) system) generates a base substance that is then used to generate the ocean alkalinity product. The control circuit controls the base-generating device such that the alkalinity product is supplied to the ocean only when (1) sufficient low/zero-carbon electricity is available, (2) it is safe to operate the base-generating device, and (3) supplying the alkalinity product will not endanger sea life. Modified BPED systems include features that facilitate autonomous system operations including enhanced maintenance cycle operations and a reduced reliance on external fresh water sources.

RELATED APPLICATIONS/PATENTS

This application is a divisional of U.S. patent application Ser. No.17/838,967, entitled “OCEAN ALKALINITY SYSTEM AND METHOD FOR CAPTURINGATMOSPHERIC CARBON DIOXIDE” filed on Jun. 13, 2022, which claimspriority from U.S. Provisional Patent Application No. 63/289,558,entitled “CONTROL OF A SYSTEM FOR CAPTURING ATMOSPHERIC CARBON DIOXIDEBY INCREASING OCEAN ALKALINITY, AND BIPOLAR ELECTRODIALYSIS SYSTEM FORCAPTURING ATMOSPHERIC CARBON DIOXIDE”, filed on Dec. 14, 2021, which isentirely incorporated herein by reference.

FIELD OF THE INVENTION

The systems, methods, and devices described herein relate to reducingatmospheric carbon dioxide (CO₂) and mitigating ocean acidification.

BACKGROUND OF THE INVENTION

As humans burn more and more fossil fuels, the resulting increasedcarbon dioxide (CO₂) concentration in Earth's atmosphere causes bothclimate change and ocean acidification. The increased atmosphericconcentrations of CO₂ and other greenhouse gasses (e.g., methane)produces climate change by trapping heat close to earth's surface,thereby increasing both air and sea temperatures. Because earth's oceansabsorb about 25% of atmospheric CO₂, and because the absorbed CO₂dissolves to form carbonic acid that remains trapped in the seawater,the increased atmospheric CO₂ concentration caused by burning fossilfuels also produces ocean acidification by way of increasing the amountof CO₂ gas dissolved in the ocean.

Both climate change and ocean acidification pose significant threats tohumans. Climate change in the form of increased global averagetemperatures can produce several dangerous effects such as the loss ofpolar ice and corresponding increased sea levels, disease, wildfires andstronger storms and hurricanes. Ocean acidification changes the oceanchemistry that most marine organisms rely on. One concern with oceanacidification is that the decreased seawater pH can lead to thedecreased survival of shellfish and other aquatic life having calciumcarbonate shells, as well as some other physiological challenges formarine organisms.

To avoid dangerous climate change, the international Paris Agreementaims to limit the increase in global average temperature to no more than1.5° C. to 2° C. above the temperatures of the pre-industrial era.Global average temperatures have already increased by between 0.8° C.and 1.2° C. The Intergovernmental Panel on Climate Change (IPCC)estimates that a ‘carbon budget’ of about 500 GtCO₂ (billion tons ofcarbon dioxide), which corresponds to about ten years at currentemission rates, provides a 66% chance of limiting climate change to 1.5°C.

In addition to cutting CO₂ emissions by curtailing the use of fossilfuels, climate models predict that a significant deployment of negativeemissions technologies (NETs) will be needed to avoid catastrophic oceanacidification and global warming beyond 1.5° C. (see “Biophysical andeconomic limits to negative CO2 emissions”, Smith P. et al., Nat. Clim.Chang. 2016; 6: 42-50). Current atmospheric CO₂ and other greenhouse gasconcentrations are already at dangerous levels, so even a drasticreduction in greenhouse gas emissions would merely curtail furtherincreases, not reduce atmospheric greenhouse gas concentrations to safelevels. Moreover, the reduction or elimination of greenhouse gas sources(e.g., emissions from long distance airliners) would be extremelydisruptive and/or expensive and are therefore unlikely to occur soon.

Therefore, there is a need to supplement emission reductions with thedeployment of NETs, which are systems/processes that serve to reduceexisting atmospheric greenhouse gas concentrations by, for example,capturing/removing CO₂ from the air and sequestering it for at least1,000 years. The need for NETs may be explained using a bathtub analogyin which atmospheric CO₂ is represented by water contained in a bathtub,ongoing CO₂ emissions are represented by water flowing into the tub, andNETs are represented by processes that control water outflow through thetub's drain. In this analogy, reduced CO₂ emission rates are representedby partially turning off the water inflow tap—the slower inflow rateprovides more time before the tub fills, but the tub's water level willcontinue to rise and eventually overflow. Using this analogy, althoughreducing CO₂ emissions may slow the increase of greenhouse gas in theatmosphere, critical concentration levels will eventually be reachedunless NETs are implemented that can offset the reduced CO₂ emissionlevel (i.e., remove atmospheric CO₂ at the same rate it is beingemitted). Moreover, because greenhouse gas concentrations are already atdangerous levels (i.e., the tub is already dangerously full), there isan urgent need for NETs that are capable of significantly reducingatmospheric CO₂ faster than it is being emitted to achieve safeatmospheric concentration levels (i.e., outflow from the tub's drainmust be greater than the reduced inflow from the tap to reduce the tub'swater to a safe level).

NETs include Direct Air Capture (DAC) approaches and Indirect OceanCapture (IOC) approaches. DAC NET approaches, which attempt to extractCO₂ directly from the atmosphere, can be broadly divided into twocategories: Nature-based DAC approaches and Technological(technology-based) DAC approaches. Nature-based DACs include Forestryand Soil Carbon Sequestration (SCS) approaches. Forestry approaches(aka, Afforestation and Reforestation) promote the expansion anddevelopment of forested land to increase the capture and storage ofatmospheric CO₂. SCS DAC approaches utilize several natural approaches(including forestry) to improve soil fertility and increase soil carbonsaturation limits. Technological DACs include Bioenergy with CarbonCapture and Storage (BECCS), which involves the utilization of biomassas an energy source and the capture and permanent storage of CO₂produced during the conversion of biomass to energy. IOC NET approachesattempt to offset greenhouse gas emissions by increasing the ocean'sability to absorb atmospheric CO₂ using various natural and/ortechnological processes such as Mineral Ocean Alkalinity Enhancement.Mineral Ocean Alkalinity Enhancement involves adding solid alkalinesubstances (e.g., crushed minerals such as olivine or lime) to seawaterto enhance the ocean's natural carbon sink function.

The above-mentioned NET approaches are problematic in that they can benot economically self-sustaining and/or pose measurability, permanence,additionality, toxicity, safety, and/or scalability problems. Forexample, in the case of existing Mineral Ocean Alkalinity Enhancementapproaches, measurability and verification are complicated byuncertainties around the dissolution kinetics of the solid alkalinesubstances, while impurities and trace metals in the solid alkalinesubstances lead to concerns about toxicity and safety for marineecosystems.

What is needed is an economically sustainable NET approach thatmeasurably and permanently reduces atmospheric CO₂ and mitigates oceanacidification and has the ability to scale to a meaningful amount of CO₂removal (i.e., on the order of gigaton of removed CO₂ per year).

SUMMARY OF THE INVENTION

The embodiments described herein are directed to an electrochemicalocean alkalinity enhancement (OAE) system and associated operatingmethod that reduces atmospheric carbon dioxide (CO₂) and mitigates oceanacidification by generating a base solution containing a fully dissolvedbase (caustic) substance and supplying the ocean alkalinity product toocean seawater at a designated outfall location, whereby the basesubstance diffuses (disperses) into the surrounding seawater.Accordingly, aspects described herein directly reverse oceanacidification (i.e., by utilizing the base substance in the oceanalkalinity product to increases the ocean seawater's alkalinity), andindirectly reduces atmospheric CO₂ (i.e., increasing the oceanseawater's alkalinity increases the ocean's ability to absorb/captureatmospheric CO₂). Moreover, because the generated base substance isfully dissolved in the ocean alkalinity product, the aspects describedherein avoid the dissolution kinetics issues (mentioned above) that areassociated with conventional Mineral Ocean Alkalinity Enhancementapproaches.

According to an aspect described herein, the OAE system includes abase-generating device that electrochemically processes an externallysupplied feedstock (saline) solution to generate a base solutioncomprising fully dissolved NaOH molecules. In some embodiments the oceanalkalinity product is then produced by mixing the base solution withsaltwater to achieve a pH that is a predetermined amount higher than theocean's seawater (e.g., in a target pH range between 8.0 and 9.0). Inanother embodiment the base solution is not mixed with seawater, butcontrollably added to the ocean directly in a safe manner. The feedstocksolution can be supplied to the OAE system from an external saltfeedstock. In some embodiments the feedstock solution may compriseseawater pumped directly from a large saltwater body (i.e., a sea, oceanor saltwater lake, which for brevity are collectively referred to hereinas “ocean” and the associated saltwater is referred to as “seawater”).However, in some embodiments, the feedstock solution comprises brinefrom a desalination plant, water recycling plant or another brine sourcethat is deployed near an ocean. In one embodiment, the electrochemicalprocess performed by the base-generating device involves dissociatingwater and salt molecules in the feedstock solution such that theresulting hydroxide and sodium ions combine to generate NaOH moleculesin the base solution. The base solution is then tested and processed(e.g., reacted with air or CO₂ and/or diluted with processed feedstocksolution, seawater or another saltwater solution) to generate the oceanalkalinity product having the target pH range. After verifying that theocean alkalinity product is within the target pH range, thebase-generating device may supply the ocean alkalinity product to theocean (e.g., by pumping the ocean alkalinity product through a transferpipe to a designated outfall location).

According to another aspect described herein, the OAE system includes acontrol circuit is operably configured to monitor input data receivedfrom multiple sources (e.g., sensors) and to control operationsperformed by the base-generating device such that the ocean alkalinityproduct is supplied to the ocean only when the monitored input dataindicates (1) sufficient low/zero-carbon electricity is available tooperably power the base substance generation and supply operationsperformed by the base-generating device, (2) the base-generating deviceis operably configured to perform the generation and supply operationssafely, and (3) supplying the ocean alkalinity product will notendanger, and is most likely to benefit, sea life in the ocean (e.g.,adjacent to the outfall location). In some embodiments the controlcircuit is a computer/processor that implements software-basedinstructions or is otherwise configured to execute a control algorithmthat continuously monitors the input data, and controls operationsperformed by the base-generating device. To maximize net carbonreduction and to minimize environmental threats, the control circuit canalso be configured to restrict base substance supplying operationsperformed by the base-generating device to (fourth) time periods whenall three conditions (1), (2) and (3) are concurrently satisfied. Insome embodiments, to maximize operating efficiency, the control circuitmay be further configured to perform automated maintenance cycles during(fifth) time periods during which conditions (1) and (2) are satisfied(i.e., low/zero-carbon electricity is available and the base-generatingdevice is capable of safely conducting the automated maintenance cycles,but when supplying the base substance may endanger sea life). In otherembodiments, certain low-power-consumption maintenance cycles (e.g.,de-scaling operations, described below) may be implemented whenlow/zero-carbon electricity is unavailable, particularly when performingthese maintenance cycles enhances operating efficiency (e.g., enhancingthe lifetime of ion exchange membranes by reducing degradation) duringsubsequent high-power-consumption operating cycles. By controllingoperations of the base-generating device in this fully automated manner,the OAE systems and methods described herein may address theadditionality issue associated with conventional approaches byrestricting high-power-consuming operations (e.g., base generation) totime periods when sufficient low/zero carbon electricity is available.The aspects described herein may also minimizes environmental impact byrestricting base-generating operations to time periods when thebase-generating device can be operated safely, and by supplying the basesubstance to an outfall location in a molecular form that reliably andpredictably disperses into the surrounding ocean seawater. The aspectsdescribed herein may also fill the need for economically sustainableNETs (carbon offset systems) by reducing costs for operation andmaintenance (i.e., reducing or eliminating the need for human operatorsand maintenance providers). Moreover, the aspects described herein maymeet the need for measurability and verification by way of utilizingocean-based sensors to verify the predictable dispersion of the basesubstance molecules into the seawater surrounding the outfall location.Finally, the permanence of the CO₂ capture approach utilized by theaspects described herein has been shown to be quite long (approximately10,000 years).

In some embodiments the base-generating device implemented in each OAEsystem includes a bipolar electrodialysis (BPED) system that processesthe externally supplied feedstock solution (e.g., seawater or brine) ina way that generates both the concentrated base solution (basesubstance) and a concentrated acid solution. In an embodiment, the BPEDsystem includes a fluid buffering system, an electrodialysis apparatus,a flow control system and a series of flow lines (i.e., tubes, pipes orother suitable fluid conduit structures). The fluid buffering system mayinclude three main buffer tanks respectively configured to store thefeedstock solution, the base solution and the acid solution. Theelectrodialysis apparatus may include a contained ion exchange stackincluding a series of salt, acid and base chambers that are respectivelyseparated by ion-permeable membranes (filters). Each salt chamber may beseparated from an adjacent acid chamber by an intervening first filtertype and separated from an adjacent base chamber by an interveningsecond filter type. The electrodialysis apparatus may also includeelectrodes that are configured to apply an electric field across(through) the salt, acid and base chambers that causes ions to passthrough the intervening filters in a predetermined manner. Duringoperation the flow control system may utilize one or more pumps todirect a salt stream from the salt buffering tank through the saltchambers of the electrodialysis apparatus by way of a salt input lineand a salt output line. Similarly, the flow control system may utilizeadditional pumps and associated inflow/outflow lines to direct an acidstream from the acid buffering tank through the acid chambers and a basestream from the base buffering tank through the base chamber. Theelectrodialysis apparatus can be configured such that the appliedelectric field causes Cl− ions to pass from the salt chambers throughthe first filters into the acid chambers, and also causes Na+ ions topass from the salt chambers through the second filters into the basechambers in a way that concentrates (increases) the amount (strength) ofacid (HCl) in the acid stream and the amount of base (NaOH) in the basestream. That is, the “outflow” acid and base streams leaving theelectrodialysis apparatus can be stronger (i.e., have a higherconcentration of acid and base substance, respectively) than the“inflow” acid and base streams supplied to the electrodialysisapparatus. Therefore, the properties of concentration and pH may changeas each acid/base fluid stream passes through the electrodialysisapparatus. Accordingly, an advantage of utilizing a BPED system in theOAE system described above is the beneficial generation of an acidsubstance that can be utilized for a variety of commercial purposes. Forexample, in some embodiments the BPED system may be operated in “feedand bleed” mode wherein some of the stronger acid stream exiting theelectrodialysis apparatus is bled off as an acid product that may becommercially utilized (e.g., processed by an electrolyzer to generatehydrogen gas, chlorine gas and/or oxygen gas) to further enhance theeconomically sustainability of the OAE system as a carbon offset system(e.g., by utilizing the hydrogen gas to generate supplementalelectricity that can be used by the OEA system).

In some embodiments the BPED system utilizes a modified flow controlsystem that facilitates automatic descaling of the base and saltchambers of an electrodialysis apparatus during maintenance cycles. Inan embodiment the modified flow control system includes a set ofthree-way valves and associated cross-feed lines that are operablyconfigured to facilitate automatic descaling operations during periodicmaintenance operation cycles. During normal base generation/supplyoperations (i.e., while the BPED system is controlled to generate andsupply base substance to the ocean), the three-way valves are controlledusing first control signals to direct salt, acid and base streamsrespectively from the salt, acid and base buffer tanks through the salt,acid and base chambers of the electrodialysis apparatus, respectively,and then back to the respective buffer tanks. In contrast, duringselected maintenance cycle operations, the three-way valves can becontrolled using second control signals such that an acid stream leavingthe acid buffer tank is diverted (i.e., by way of correspondingcross-feed lines) through the salt chamber and/or the base chamber andthen returns to the acid buffer tank. As it passes through the salt andbase chambers, the diverted acid stream may serve to dissolve and removescaling that gradually builds up on the corresponding surfaces of theintervening bipolar filters and impedes the efficient transfer of ionsbetween adjacent chambers. By utilizing a BPED system having a flowcontrol system that is modified in this manner, the systems and methodsdescribed herein may further enhance the economic sustainability of theOAE system by facilitating automatic maintenance operations that enhancethe operating efficiency of the BPED system (i.e., by way of performingperiodic descaling of the electrodialysis apparatus without the need forhuman involvement).

In some embodiments the BPED system is further modified to include apretreatment unit that is configured to reduce or eliminate the OAEsystem's dependence on a fresh water supply by at least partiallydesalinating (i.e., removing at least some of the salt and otherdivalent cations from) an externally supplied feedstock solution (i.e.,seawater or brine), and then utilizing the resulting reduced-salt fluidto generate the acid solution and/or the base solution (e.g., bysupplying the reduced-salt fluid to the acid (second) and/or base(third) buffer tanks instead of fresh water from an external source). Insome embodiments, a reverse osmosis (pretreatment) unit processes theexternally supplied feedstock solution (e.g., seawater) to generate apermeate (reduced-salt fluid) and a concentrate (i.e., a high-salt fluidhaving a higher salt concentration than the feedstock solution and asignificantly higher salt concentration than the permeate). In theseembodiments, the concentrate (high-salt fluid) is used as the feedstocksolution supplied to the salt (first) buffer tank and the permeate isdirected to both the acid (second) and base (third) buffer tanks (i.e.,to replace liquid volume reductions caused by the above-mentionedfeed-and-bleed operations, and to maintain optimal solutionconcentrations). In other embodiments, brine is used as the externallysupplied feedstock solution, and a chemical acid concentrator(pretreatment) unit is configured to utilize the brine to concentrate aportion of the strong acid stream leaving the electrodialysis apparatus,and a reduced-salt fluid produced by the acid concentration process isutilized as the feedstock solution provided to the salt (first) buffertank. In cases where the salt content of the reduced-salt fluid isacceptably low, a portion of the reduced-salt fluid may also be directedto both the acid (second) buffer tank and the base (third) buffer tank(i.e., to replace liquid volume reductions instead of fresh water). Inother cases (e.g., those requiring relatively pure concentrated acidsolution), a portion of the reduced-salt fluid may be supplied to thebase (third) buffer tank, and fresh or deionized water may be suppliedto the acid (second) buffer tank. Utilizing a BPED system that ismodified to include one of the pretreatment arrangements mentioned abovemay further reduce the operating costs of OEA systems formed inaccordance with the aspects described herein by significantly reducingor eliminating the need for a fresh water supply, which can represent asignificant operating expense in remote settings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings, where:

FIG. 1 is a diagram depicting an electrochemical ocean alkalinityenhancement (OAE) system according to an embodiment;

FIG. 2 is a flow diagram depicting a control method utilized to controlthe OAE system of FIG. 1 according to another embodiment;

FIG. 3 is a modified diagram depicting a bipolar electrodialysis (BPED)system that may be utilized as a base-generating device by the OAEsystem of FIG. 1 according to an embodiment;

FIG. 4 is a modified diagram depicting an electrodialysis apparatus thatmay be utilized by the BPED system of FIG. 3 according to an exemplaryembodiment;

FIG. 5 is a diagram depicting a modified BPED system according toanother embodiment;

FIGS. 6A and 6B are modified diagrams depicting the BPED system of FIG.5 during base-generating operations and maintenance operations,respectively;

FIG. 7 is a diagram depicting a modified BPED system including areverse-osmosis-type pretreatment unit according to another embodiment;

FIG. 8 is a diagram depicting a modified BPED system including achemical-acid-concentrator-type pretreatment unit according to anotherembodiment;

FIG. 9 is a diagram depicting a modified BPED system including achemical-acid-concentrator-type pretreatment unit according to anotherembodiment; and

FIG. 10 is a simplified diagram depicting an alkalinity productgeneration unit according to another embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

The methods and systems described herein relate to an improvement inmethods and systems for reducing atmospheric carbon and mitigating oceanacidification. The following description is presented to enable one ofordinary skill in the art to make and use the methods and systemsdescribed herein as provided in the context of specific embodiments.Various modifications to the embodiments will be apparent to those withskill in the art, and the general principles defined herein may beapplied to other embodiments. Therefore, the methods and systemsdescribed herein are not intended to be limited to the particularembodiments shown and described but are to be accorded the widest scopeconsistent with the principles and novel features herein disclosed.

FIG. 1 shows a generalized OAE system 100 that is configured to capturecarbon dioxide (CO₂) from earth's atmosphere and mitigate oceanacidification by generating and supplying an ocean alkalinity product113-OUT (i.e., an aqueous solution comprising salt and a base (caustic)substance and having a pH>8) to seawater 51 at an outfall location 50-1.As indicated in the lower right portion of FIG. 1 , the base substancesupplied with alkalinity product 113-OUT may gradually diffuse(disperses) into seawater 51 surrounding outfall location 50-1 (e.g., asdepicted by region 54 in FIG. 1 ), and the resulting increasedalkalinity of seawater 51 may reduce ocean acidification and increasesthe ocean's ability to absorb/capture atmospheric CO₂ (e.g., fromatmospheric region 56 located over seawater 51). As described below, OAEsystem 100 carefully controls the generation and supply of oceanalkalinity product 113-OUT to prevent harm to sea life caused bydangerously high seawater pH levels near outfall location 50-1, whichmay occur if the base substance in ocean alkalinity product 113-OUT issupplied in an uncontrolled (e.g., continuous or highly concentrated)manner into seawater 51. While outfall location 50-1 is depicted as asingle location, in practice, alkalinity product 113-OUT may be suppliedto ocean 50 at multiple locations in space and time.

In some embodiments, OAE system 100 receives and processes an externallysupplied feedstock (salt) solution 111-IN to generate alkalinity product113-OUT, and transports (supplies) alkalinity product 113-OUT to outfalllocation 50-1 by way of being pumped through a transport pipe 52. Insome embodiments externally supplied feedstock solution 111-IN issupplied to OAE system 100 from an external salt feedstock source 60. Insome embodiments, feedstock solution 111-IN includes seawater (oceanwater) 50-1 that is pumped directly from ocean 50. In other embodiments,feedstock solution 111-IN comprises brine 66 generated by a brine source65 (e.g., a desalination plant or a water recycling plant that processesseawater 51-2 and generates brine 66 as a byproduct).

Referring to the lower portion of FIG. 1 , OAE system 100 may include abase-generating device 110, a control circuit 180 and a powerdistribution circuit 190.

Base-generating device 110 may comprise a device/system that isconfigured to (i.e., when supplied with sufficient operating power) bothgenerate alkalinity product 113-OUT by processing feedstock solution111-IN and to supply (e.g., pump) alkalinity product 113-OUT to outfalllocation 50-1 (e.g., by way of transfer pipe 52). In some embodimentsdevice 110 is implemented using any of the features described below withreference to FIGS. 3 to 9 . In other embodiments, device 110 may beanother device or system capable of generating and supplying alkalinityproduct 113-OUT to outfall location 50-1.

Control circuit 180 can be an electronic device (e.g., acomputer/processor or dedicated electronic device) that implementssoftware-based instructions or is otherwise configured to execute acontrol algorithm that controls base-generating device 110 and anoptional power distribution circuit 190 in a fully autonomously manner(e.g., as described below with reference to FIG. 2 ). In one embodiment,control circuit 180 controls operations performed by base-generatingdevice 110 such that alkalinity product 113-OUT is generated/suppliedonly during time periods when the control algorithm determines thatthree predefined conditions are satisfied: (1) sufficientlow/zero-carbon electricity (LCE) is available to operably powerbase-generating device 110, (2) base-generating device 110 is operablyconfigured to safely generate and supply alkalinity product 113-OUT tooutfall location 50-1, and (3) supplying alkalinity product 113-OUT willnot endanger, and is most likely to benefit, sea life in seawater 51(e.g., adjacent to the outfall location 50-1). To facilitate determiningthat these conditions are satisfied, control circuit 180 can beconfigured to receive and process various input data signals receivedfrom sensors and/or other data sources. In an embodiment, these variousinput data signals may include an LCE availability data signal 181, abase-generating device operational safety data signal 182, and an oceanchemistry data signal 183 that may be supplied by way of directconnection or by a local or wide area network (e.g., by way of the WorldWide Web (Internet) 90) to control circuit 180. The sources and contentof data signals 181, 182 and 183 are described in the followingparagraphs.

LCE availability data signal 181 can indicate whether sufficientlow/zero-carbon electricity LCE is available to facilitate thegeneration and supply of alkalinity product 113-OUT by base-generatingunit 110. To maximize atmospheric carbon dioxide reduction by addingalkalinity to seawater 51, low or zero carbon intensity electricity LCE(herein referred to as “low/zero-carbon electricity”) generated by oneor more LCE sources 80 can be utilized by base-generating unit 110 togenerate/supply alkalinity product 113-OUT. In some embodiments, LCEdata signal 181 is generated using known techniques such that itprovides some measure of the composition of power supplied by each powergeneration source coupled to OAE system 100 (e.g., by way of a powergrid 95). That is, electrical power supplied to OAE system 100 frompower grid may include both LCE produced by one or more LCE sources 80(e.g., wind, solar, tidal, hydro, clean hydrogen, nuclear, geothermal,or BECCS) and other electrical power P which may be distinguished fromcarbon dioxide emitting power generation sources such as coal or gasdriven turbines. LCE availability data signal 181 can indicate whetherthe total power LCE/P supplied to OAE system 100 includes sufficientlow/zero-carbon electricity LCE to power base-generating device 110. LCEavailability data signal 181 may be generated using one or more sensorsS1, or may be obtained from such sources such as data from federal poweragencies, state power agencies, balancing authorities, third partyenergy aggregators, power purchase agreements, power producers, localutilities, state utilities commissions, or other available data streamsor may be derived from other available data that can indicate supply ordemand of electricity at a given time or place in an energy gridincluding weather or production data streams. In some embodiments LCEavailability data signal 181 may also include spot pricing informationthat may be used to control the operations of OAE system 100 in a waythat maximizes efficiency and minimizes operating costs. Energy pricinginformation may be accessible in real-time or in a futures market on alocational, marginal level through local energy markets platforms,authorities or commercial market participants. Transmission of LCEavailability data signal 181 may be by wired connection (e.g., directlyfrom sensor S1 or dedicated LCE source 80 or by way of Internet 90) orby wireless transmission. In some embodiments, the future LCE datasignal (for example the signal in the next hour or next 24 hours) may beestimated using predictive modeling and this information will be used tooptimize planned system uptime.

Operational safety signal 182 generally indicates whetherbase-generating device 110 is operably configured to safely generatebase substance 113, or, for example, damage to OAE system 100 may resultfrom the generation and supply of alkalinity product 113-OUT bybase-generating device 110. In one embodiment, operational safety signal182 may be generated by one or more sensors S2 that monitor associatedparameters (e.g., pressure, temperature) associated with the operationof base-generating device 110, and allow the control algorithm tooperate device 110 within certain safety and environmental healthconstraints or requirements, or to cause device 110 to enter a safeoperating state (e.g., turning off power or shutting valves and/oralerting local authorities) in response to various safety anomalies(e.g., leaks, fire, overcurrent, thermal or seismic) indicated byoperational safety signal 182. System functions and components that maybe controlled include power, voltage, current, pump speeds, controlvalves, maintenance cycles, tank levels, as well as system duty cycle(on or off), or selecting which individual membranes, modules, or stacksto utilize at a given time. In alternative embodiments controlling thesesystem functions and components may be operated remotely by an operatoror may be fully autonomous (i.e., without the need for continuous humansupervision) to enable lights-out operation.

Seawater chemistry data signal 183 generally indicates whethergenerating and supplying alkalinity product 113-OUT to outfall location50-1 may endanger, or benefit, sea life. In some embodiments, at leastpart of seawater chemistry data signal 183 is generated by one or moresensors S3 located in or near seawater 51 adjacent to outfall location50-1, and includes measured seawater chemistry data such as, but notlimited to, pH, total dissolved inorganic carbon (DIC), totalalkalinity, partial pressure of CO₂ (pCO₂), conductivity, salinity,temperature, pressure, refractometry, flow rates, density, or any otherproperties thereof. In some embodiments seawater chemistry data signal183 also includes data generated using ocean and other environmentalmodels configured to predict ocean currents, weather, tides, biologicalproductivity, location and type of marine organisms, and demand forelectricity. In some embodiments, the performance of OAE system 100 maybe monitored by measuring seawater 51 near outfall location 50-1 toachieve an effective mixture of alkalinity product 113-OUT in seawater51. Transmission of seawater chemistry data signal 183 may be by wiredconnection (e.g., by a wire directly connecting sensor(s) S3 to controlcircuit 180 or by way of Internet 90) or by wireless transmission.

The control algorithm executed by control circuit 180 can receive andprocess data signals 181, 182 and 183 (e.g., in the manner depicted inthe flow diagram of FIG. 2 , discussed below) to continuously controlbase generating device 110 and to optimize overall system parameters to,for example, minimize cost, or maximize throughput, or maximize uptime,or minimize impact on sea life, or minimize flow rates, or predict whento run and when to remain idle, or when to perform planned maintenance,or periodic membrane cleaning cycles. In some embodiments, the controlalgorithm implemented by control circuit 180 utilizes machine learningand artificial intelligence.

Optional power distribution circuit 190 can be configured to distributeexternally supplied electrical power LCE/P to base-generating device 110in response to control signal 187 generated by control circuit 180. Thatis, when the control algorithm determines that the three conditionsmentioned above are satisfied, control circuit 180 can assert controlsignal 187. In one embodiment, when low/zero-carbon power LCE is notavailable, power P can be supplied by power distribution circuit 190 tocontrol circuit 180 to facilitate continuous processing of the controlalgorithm described herein. In some embodiments, power P is alsosupplied by power distribution circuit 190 to base generating unit 110to facilitate certain low-power-consumption maintenance operations(e.g., the descaling operation described below with reference to FIGS.5, 6A and 6B).

As indicated at the bottom of FIG. 1 , the various components of OAEsystem 100 may be disposed within a modular system housing 109 tofacilitate transport and placement near a salt feedstock 60 and seawater51, and to protect OAE system 100 during operation. In some embodiments,housing 109 is an otherwise standard shipping container that is modifiedto include various access ports configured to facilitate operableconnections of the various system components to externalsources/destinations. In the depicted example, a salt input port 101 isprovided to facilitate the transfer of feedstock solution 111-IN intohousing 109 for receipt by base-generating device 110, a base outputport 103 is provided to facilitate the transfer of alkalinity product113-OUT supplied by base-generating device 110 to transfer pipe 52, adata port 105 is provided to transfer externally generated signals 181and 183 to control circuit 180, and a power port 106 is provided totransfer low/zero-carbon electricity LCE and other power P to powerdistribution circuit 190. In other embodiments housing 109 may beomitted; for example, OAE system 100 may be integrated into abrine-producing industrial process facility (e.g., deployed within abuilding or other structure containing a desalination plant), therebyobviating the need for a separate protective housing.

FIG. 2 depicts a generalized method for controlling operations performedby OAE system 100 (FIG. 1 ) such that it captures atmospheric carbondioxide and mitigates seawater acidification. In one embodiment, themethod is performed using computer-based instructions that form acontrol algorithm executed by the processor of control circuit 180 (FIG.1 ). That is, control circuit 180 can be operably configured andutilized to monitor various signals (e.g., sensor/data signals 181, 182and 183), and to restrict operations of base-generating device 110 (FIG.1 ) to time periods when specific operating conditions are present.

Referring to start block 201 (top of FIG. 2 ), the method may begin by(decision block 210) monitoring the availability of low/zero-carbonelectricity (e.g., by monitoring data signal 181 received from sensor(s)S1, described above, and/or other control signal sources). Wheninsufficient low/zero-carbon electricity is available (NO branch fromblock 210), control can be returned to block 201, thereby effectivelypreventing operations performed by base-generating device 110 wheninsufficient low/zero-carbon electricity is available. When sufficientlow/zero-carbon electricity is available (YES branch from block 210),control can be passed to decision block 220. For clarity, each portionof time during which sufficient low/zero-carbon electricity is availableis referred to as a first time period. As established by block 210, thecontrol algorithm may restrict the flow of operating power tobase-generating device 110 such that base-generating device 110 receivessufficient operating power (e.g., to generate base substance) onlyduring first time periods (i.e., when sufficient low/zero-carbonelectricity at sufficiently low cost is available from one or morelow/zero-carbon electricity sources 80).

Referring to decision block 220, the control algorithm may nextdetermine whether base-generating device 110 can be operated safely(e.g., by monitoring data signal 182 received from sensor(s) S2,described above, and/or other signals generated by safety anomalysensors or other sources). When the various safety signals indicate thatbase-generating device 110 cannot be operated safely, control may passon the NO branch from block 220 back to start block 201. For example, ifoperational safety signal 182 indicates that device 110 is disassembledfor repair/maintenance or indicates that a dangerous situation may occurif device 110 were actuated, then the control algorithm prevents device110 from operating, even though sufficient low/zero-carbon electricityis available, by way of diverting control back to start block 201. Whenthe various safety signals indicate that base-generating device 110 canbe operated safely, the control algorithm may pass control on the YESbranch from block 220 to block 230. For clarity, each portion of timeduring which the control algorithm determines that base-generatingdevice 110 can be operated safely is referred to as a second timeperiod. Note that each second time period can occur during a first timeperiod only. Accordingly, the control algorithm effectively restrictsoperations performed by base-generating device 110 to second timeperiods when both sufficient low/zero-carbon electricity is availableand base-generating device 110 can be operated safely.

Referring to decision block 230, after verifying that sufficientlow/zero-carbon electricity is available and that operatingbase-generating device 110 would be safe, the control algorithm may nextdetermine whether supplying alkalinity product 113-OUT to seawater 51may endanger, or benefit, sea life near outfall location 50-1. In oneembodiment, control circuit 180 monitors ocean chemistry signal(s) 183generated by sensor(s) S3 and/or data 183A to identify time periodsduring which supplying alkalinity product 113-OUT to seawater 51generates zero or minimal risk of harm to sea life. In some embodiments,data 183A may include one or more of (a) optional environmentalcomputational models capable of verifying that the alkalinity ofseawater 51 near outfall location 50-1 (as measured by sensor S3) ischanging the local seawater chemistry in an expected manner, thespreading of this added alkalinity in space and time and itsequilibration with, and removal of, atmospheric CO₂, (b) pH,conductivity, volumetric flow and other sensor data received from basegenerating device 110 that indicate the availability and chemistry ofalkalinity product 113-OUT, and/or (c) seawater chemistry data fromadditional ocean-based sensors (not shown) that may be placed atincreasing distances from outfall location 50-1 to verify the modelpredictions. When the ocean chemistry signal(s) 183 and/or environmentalmodel data 183A indicate that alkalinity product 113-OUT can be suppliedsafely, the control algorithm passes control on the YES branch fromblock 230 to block 240. For clarity, each portion of time during whichthe control algorithm determines that base-generating device 110 cansafely supply alkalinity product 113-OUT is referred to as a third timeperiod, where each third time period can occur during a first timeperiod and a second time period only. Conversely, when either of oceanchemistry signal(s) 183 and/or environmental model data 183A indicatesthat supplying alkalinity product 113-OUT to seawater 51 endangers sealife, control may pass on the NO branch from block 230 to block 250. Forexample, if ocean chemistry signal(s) 183 indicate that the pH atoutfall location 50-1 is too high to safely receive additional basesubstance, then the control algorithm temporarily can prevent device 110from supplying additional alkalinity product 113-OUT to outfall location50-1, even though sufficient low/zero-carbon electricity is availableand device 110 can be operated safely.

Referring to block 240, the operations performed by base-generatingdevice 110 can be controlled (e.g., by signal 185-1) such that thebase-generating device 110 supplies alkalinity product 113-OUT toseawater 51 only during a fourth time period, the fourth time periodcomprising concurrent portions of all of the first, second and thirdtime periods (mentioned above). That is, the control algorithm maycontrol base-generating device 110 such that alkalinity product 113-OUTmay be supplied to the ocean 50 when the input data (e.g., signals 181,183 and 183) received by control circuit 180 indicates (1) sufficientlow/zero-carbon electricity is available to operably powerbase-generating device 110, (2) base-generating device 110 is operablyconfigured to safely generate and supply alkalinity product 113-OUT, and(3) supplying alkalinity product 113-OUT will not endanger, and is mostlikely to benefit, sea life in the ocean 50 (e.g., adjacent to theoutfall location 50-1).

Referring to block 250, in some embodiments the operations performed bybase-generating device 110 can be controlled (e.g., by signal 185-2)such that the base-generating device 110 performs one or more scheduledmaintenance cycles during fifth time periods, where each fifth timeperiod includes concurrent portions of the above mentioned first andsecond time periods but does not occur during a third time period (i.e.,during periods when LCE power is available and it is safe to operate theBPED, but when supplying alkalinity product 113-OUT may endanger sealife). That is, the control algorithm executed by control circuit 180may restrict the operations performed by device 110 to scheduledmaintenance or other non-base-generating operations when the oceanalkalinity signals 183 and/or environmental model signals 183A indicatethat supplying alkalinity product 113-OUT to seawater 51 may endangersea life. In some embodiments, the scheduled maintenance cycles mayinclude a maintenance cycle in which base-generating device 110 isoperated to generate alkalinity product 113-OUT but stores the basematerial in an outgoing buffer tank during the fifth time periods (i.e.,base-generating device 110 is not operated in a way that supplies basesubstance to the ocean during these maintenance cycles), and thenbase-generating device 110 is operated subsequently occurring fourthtime period to pump (supply) the stored base substance from the outgoingbuffer tank to the ocean. In other embodiments, the control algorithmmay be configured to use data indicating the state of the outgoing basebuffer tank, carbon market data, and ocean chemistry status data todetermine, based on predictions of rate of base dispersal into the oceanin the near future and how full the outgoing base buffer tank is,whether to cause base-generating device 110 to generate base substanceat that moment, or perform non-base-generating maintenance cycleoperations such as the descaling/clean-in-place operation (describedbelow with reference to FIG. 6B), or simply keep the system idle if thatis the optimum action.

By configuring control circuit 180 (FIG. 1 ) to implement the methodshown in FIG. 2 and described above, control circuit 180 may provide aclosed loop control arrangement that increases the operating efficiencyof OAE system 100 and reduces the cost of CO₂ capture by way of allowingOAE system 100 to run autonomously and continuously. This arrangementalso addresses the additionality issue associated with conventionalapproaches by restricting high-power-consuming operations (e.g., basegeneration) to time periods when sufficient low/zero carbon electricityis available, minimizes environmental impact by restrictingbase-generating operations to time periods when base-generating device110 can be operated safely, and by generating alkalinity product 113-OUTwith molecular base substance that reliably and predictably dispersesfrom region 54 into surrounding seawater 51, and meets the need formeasurability and verification by way of utilizing ocean-based sensor S3to verify the predictable dispersion of the base substance molecules.Using established permanence calculating methods, the CO₂ captureapproach described herein may have a permanence of approximately 10,000years. That is, the durability of CO₂ storage in the ocean using theapproach described herein is essentially equal to the residence lifetimeof excess alkalinity added to seawater, which can be calculated bydividing the total alkalinity (TA) concentration (3×10⁶ Tmol alkalinity)by the approximately 33 Tmol/yr TA input into the ocean through rivers(see Cai et al., Continental Shelf Research, 28, 1538-1549, 2008). Thiscalculation gives a residence estimate of about 100,000 years, assupported by the conclusions of Renforth et al., Rev. Geophys., 55,636-674, 2017. However, there are reasons to believe that the removal ofalkalinity is proportional to the degree of supersaturation rather thanthe concentration. This, in turn implies that excess alkalinity mighthave a residence time of around 10,000 years, shorter than the residencetime of alkalinity.

FIG. 3 shows a generalized bipolar electrodialysis (BPED) system 110Athat generally includes a fluid buffering system 120A, anelectrodialysis apparatus 130A, a flow control system 140A and a seriesof flow lines that are described in additional detail below. Asexplained in the following paragraphs, BPED system 110A may generateboth an alkalinity product 113A-OUT and an acid substance 112A-OUT byprocessing an externally supplied feedstock solution (e.g., seawater50-1 or brine 66 from salt feedstock 60, as described above withreference to FIG. 1 ). In some embodiments, BPED system 110A may beutilized by OAE system 100 in place of base-generating device 110 (FIG.1 ), whereby operations performed by BPED system 110A may be controlledin accordance with the method described above with reference to FIG. 2 .

Referring to the upper portion of FIG. 3 , fluid buffering system 120Acan include at least three main buffer tanks: a salt (first) buffer tank121A-1 utilized to receive and store feedstock (salt) solution 111A, anacid (second) buffer tank 121A-2 utilized to store an acid solution112A, and a base (third) buffer tank 121A-3 utilized to store a basesolution 113A. In an embodiment, each buffer tank 121A-1 to 121A-3 canbe implemented using a standard 1000L IBC caged tote tank, where saltbuffer tank 121A-1 includes a plastic containment unit 122A-1 having aninflow port 123A-1 and an outflow port 124A-1, acid buffer tank 121A-2includes a plastic containment unit 122A-2 having an inflow port 123A-2and an outflow port 124A-2, and base buffer tank 121A-3 includes aplastic containment unit 122A-3 having an inflow port 123A-3 and anoutflow port 124A-3. In other embodiments, such as those described belowwith reference to FIGS. 7 to 9 , fluid buffering system 120A may bemodified to include one or more additional buffer tanks that may beutilized to store, for example, fresh or deionized water or intermediatesolutions utilized by BPED system 110A. In some embodiments additionalbuffer tanks may be utilized to store previously generated basesubstance and acid substance solutions, thereby allowing the controlalgorithm to decouple the best time to generate acid and base substances(e.g., when electricity carbon intensity and price are most favorable)from the best time to supply the base substance into the ocean (i.e., asdetermined at least partially by data from seawater chemistry sensors).

Electrodialysis apparatus 130A may utilize known electrochemicaltechniques to split NaCl (salt) molecules provided in feedstock solution111A into Na+ and Cl− ions, to enhance (i.e., decrease the pH of) acidsolution 112A by transferring the Cl− ions from feedstock solution 111Ato acid solution 112A, and to enhance (i.e., increase the pH of) basesolution 113A by transferring the Na+ ions from feedstock solution 111Ato base solution 113A. As depicted in greatly simplified form in FIG. 3, electrodialysis apparatus 130A may include a salt chamber 131A, anacid chamber 132A and a base chamber 133A that are arranged in seriesand collectively form an ion exchange stack 134A, where each pair ofadjacent chambers is separated by an intervening ion-permeable membrane(filter) 135A-1 and 135A-2 (i.e., membrane 135A-1 separates acid chamber132A from adjacent salt chamber 131A, and membrane 135A-2 separates saltchamber 131A from adjacent base chamber 133A). Ion exchange stack 134Acan be surrounded by a water-tight containment housing (not shown) tofacilitate the flow of feedstock solution 111A through salt chamber131A, the flow of acid solution 112A through acid chamber 132A, and theflow of base solution 113A through base chamber 133A. To achieve apredetermined electrochemical process, a cathode 138A− and an anode138A+ may be disposed at opposite ends of ion exchange stack 134A andgenerate an electric field through the chambers in response to anapplied voltage differential provided by a suitable voltage source VS,thereby electrochemically processing the salt, acid and base streams inthe manner described in additional detail below.

Flow control system 140A can include various control elements (e.g.,pumps, valves etc.) that are collectively configured to direct streamsof the salt, acid and base solutions from buffer tanks 121A-1 to 121A-3through corresponding chambers of electrodialysis apparatus 130A andthen back to buffer tanks 121A-1 to 121A-3 by way of associated conduits(flow lines). For example, a salt stream 111A-1 comprises a portion offeedstock solution 111A that exits (flows from) salt buffer tank 121A-1by way of outflow port 124A-1 and is directed into salt chamber 131A byway of salt inflow line 151A-1 and a first pump 145A-11. A salt stream111A-2 may comprise processed (depleted salt) feedstock solution exitingsalt chamber 131A by way of salt outflow line 152A-1, with a firstportion 111A-21 being returned to salt buffer tank 121A-1 by way ofoptional three-way valve 146A-1, a second pump 145A-12 and salt returnline 153A-1. Similarly, acid stream 112A-1 may exit acid buffer tank121A-2 and is directed into acid chamber 132A by way of acid inflow line151A-2 and a pump 145A-21, and acid stream 111A-2 exits acid chamber132A by way of acid outflow line 152A-2, with a first portion 112A-21being returned to acid buffer tank 121A-2 by way of optional three-wayvalve 146A-2, a pump 145A-22 and acid return line 153A-2. Similarly,base stream 113A-1 may exit base buffer tank 121A-3 and is directed intobase chamber 133A by way of base inflow line 151A-3 and a pump 145A-31,and a portion 113A-21 of base stream 113A-2 exiting base chamber 133A byway of base outflow line 152A-3 is returned to base buffer tank 121A-3by way of three-way valve 146A-3, pump 145A-32 and base return line153A-3. As indicated at the bottom of FIG. 3 , in some embodimentsexternally supplied feedstock solution 111A-IN is fed from an externalsource (e.g., from salt feedstock 60 as shown in FIG. 1 ) andtransmitted with depleted salt stream portion 111A-21 to salt buffertank 121A-1 by way salt return line 153A-1. In a similar manner, in someembodiments water may be supplied from one or more external sources toreplace the outflow volumes represented by acid sub-stream 112A-22 andbase sub-stream 113A-22. For example, in some embodiments basegenerating device 110A may be utilized to process a brine streamgenerated by a desalination (or water treatment) plant, and fresh watergenerated by the desalination plant may be supplied to base buffer tank121A-3 and/or acid buffer tank 121A-2 to replace the outflow volumesrepresented by base sub-stream 113A-22 and acid sub-stream 112A-22.

As mentioned above and described in additional detail below withreference to FIG. 4 , the compositions of the acid and base solutionsmay change (strengthen) as they pass through electrodialysis apparatus130A during base-generating operations. That is, the acidity of acidstream 112A-2 leaving electrodialysis apparatus 130A may be relativelystrong in comparison to the acidity of acid stream 112A-1 due to itshigher acid concentration (i.e., due to the addition of HCl moleculesformed in the acid solution passing through acid chamber 132A).Similarly, the pH of base stream 113A-2 may be higher than that ofstream 113A-1 due to the addition of NaOH molecules as the base solutionpasses through base chamber 133A). Accordingly, for descriptive purposesacid streams 112A-1 and 112A-2 are referred to herein as weak acidstream 112A-1 and strong acid stream 112A-2, and base streams 113A-1 and113A-3 are referred to herein as weak base stream 113A-1 and strong basestream 113A-2. For similar reasons, salt streams 111A-1 and 111A-2 arereferred to as strong salt stream 111A-1 and depleted salt stream111A-2, respectively, to indicate that salt is removed from thefeedstock solution as it passes through salt chamber 131A.

During base-generating operations, electrodialysis apparatus 130A canutilize low/zero-carbon electricity LCE received, for example, frompower distribution circuit 190 (see FIG. 1 ), to generate both strongacid stream 112A-2 and strong base stream 113A-2 by processing strongsalt stream 111A-1 as described herein. In some embodiments, BPED system110A is operated in a “feed and bleed” mode wherein portions(sub-streams) of both strong acid stream 112A-2 and strong base stream113A-2 are bled off (diverted) for use in the generation of alkalinityproduct 113A-OUT or other purposes. For example, in some embodimentsstrong acid stream 112A-2 is divided such that a first acid sub-stream112A-21 is directed back to acid buffer tank 121A-2 and a second acidsub-stream 112A-22 is directed out of BPED system 110A for use as anacid product 112A-OUT by way of three-way valve 146A-3 and an associatedpump 145A-32. Similarly, strong base stream 113A-2 is divided into twosub-streams by three-way valve 146A-3, with a first base sub-stream113A-21 being directed back to base buffer tank 121A-3, and a secondbase sub-stream 113A-22 being directed to an alkalinity productgeneration unit 147A by way of three-way valve 146A-3. As described inadditional detail below with reference to FIGS. 10 and 11 , alkalinityproduct generation unit 147A can be configured to generate oceanalkalinity product 113A-OUT by processing base sub-stream 113A-22 (e.g.,mixing with a second portion 111A-22 of depleted salt stream 111A-2) andverifying that alkalinity product 113A-OUT has a pH level that suitablefor mixing with seawater before being pumped to ocean 50 (e.g., by wayof pump 145A-33).

FIG. 4 shows a portion of a BPED system 110B including anelectrodialysis unit 130B that includes an ion exchange stack 134B, aninput manifold 136B-1, an output manifold 136B-2 and an electrolytesolution circulation system 139B. Electrodialysis unit 130B may provideadditional details regarding the multiple acid, salt and base chambersdescribed above with reference to electrodialysis unit 130A (FIG. 3 ).That is, in some embodiments electrodialysis unit 130A (FIG. 3 ) isconfigured to include the features and details of electrodialysis unit130B.

Ion exchange stack 134B may include multiple acid, salt and basechambers respectively indicated by “ACID”, “SALT”, and “BASE” disposedin a repeating series arrangement between two end chambers 137B-1 and137B-2. Each of the acid, salt and base chambers of ion exchange stack134B may function as described above with reference to acid chamber132A, salt chamber 131A and base chamber 133A, respectively, to processa corresponding portion of one of the acid, salt and base solutionstreams directed through ion exchange stack 134B by way of inputmanifold 136B-1 and output manifold 136B-2. That is, input manifold136B-1 may split weaker acid stream 112B-1 (which is received from anacid buffer tank 121-2 (not shown) by way of acid inflow line 151B-2)such that a portion of the acid stream passes through each acid chamber.Similarly, input manifold 136B-1 may split weaker base stream 113B-1(which is received from a base buffer tank 121-3 (not shown) by way ofbase inflow line 151B-3) and splits salt stream 111B-1 (which isreceived from a salt buffer tank 121-1 (not shown) by way of salt inflowline 151B-1) such that a portion of the base stream passes through eachbase chamber and a portion of the salt stream passes through each saltchamber. End chambers 137B-1 and 137B-2 may function to conduct anelectrolyte solution indicated by “ES” for purposes described below.

Ion exchange stack 134B may include four types of ion permeablemembranes that are respectively disposed between adjacent acid, salt,base and end chambers and facilitate the ion transfer process utilizedto strengthen the base stream and the salt stream during operation ofBPED 110B (i.e., when ion exchange stack 134B receives an electric fieldgenerated applying voltage potentials V+ and V− to anode 138B+ andcathode 138B−, respectively). The four types of membranes are indicatedin FIG. 4 using the prefixes “A”, “K”, “B” and “F”, where membranes A1to An are anion exchange membranes, membranes K1 to Kn are cationexchange membranes, membranes B1 to Bn are bipolar membranes, andmembranes F1 and F2 are end membranes having characteristics describedbelow. Anion exchange membrane materials, cation exchange membranematerials and bipolar membrane materials capable of functioning asdescribed below can be used. In one embodiment membranes A1 to An, K1 toKn and B1 to Bn are implemented using a stack of cell trebles, whereeach cell treble includes an anion exchange membrane, a cation exchangemembrane and a bipolar membrane. Anion exchange membranes A1 to Anrepresent a first membrane type that is configured to facilitate thetransfer of Cl− ions from each salt chamber into an adjacent acidchamber. For example, the elongated bubble at the bottom of FIG. 4depicts the transfer of a first Cl− ion from salt chamber 131B-1 to acidchamber 132B-1 through membrane A1, and the transfer of a second Cl− ionfrom salt chamber 131B-2 to acid chamber 132B-2 through membrane A2.Cation exchange membranes K1 to Kn represent a second membrane type thatfacilitates the transfer of Na+ ions from each salt chamber into anadjacent base chamber. For example, the elongated bubble at the bottomof FIG. 4 depicts the transfer of a Na+ ion from salt chamber 131B-1 tobase chamber 133B-1 through membrane K1. Bipolar membranes B1 to Bnrepresent a third membrane type that facilitates the transfer ofhydrogen ions H+ from each base chamber into an adjacent acid chamberand the transfer of hydroxide ions OH− from the adjacent acid chamberinto the adjacent base chamber. For example, the elongated bubble at thebottom of FIG. 4 depicts the transfer of an H+ ion from base chamber133B-1 to acid chamber 132B-2 through membrane B1, and the transfer ofan OH− ion from acid chamber 132B-2 to base chamber 133B-1 throughmembrane B1. In some embodiments, membrane B1 includes a catalyst layersandwiched between a cation exchange layer and an anion exchange layer,with the catalyst layer functioning to dissociate water molecules thatdiffuse into membrane B1 from either acid chamber 132B-2 or base chamber133B-1, the cation exchange layer functioning to pass H+ ions of thedissociated water molecules into acid chamber 132B-2, and the anionexchange layer functioning to pass OH− ions of the dissociated watermolecules into base chamber 133B-1. Note the suffix “n” is used withreference to the various membranes and chambers merely to signifymultiple iterations of each membrane/chamber type (e.g., references to“133 n”, “Kn” and “Bn” are not intended to mean that there are anidentical number of base chambers, membranes B and/or membranes K).Membranes F1 and F2 may facilitate or reject the transfer of Na+ ionsfrom each end chamber into an adjacent acid, base, or salt chamberdepending on the order of the cell treble stack. Membranes F1 and F2 maybe Nafion, cation exchange, anion exchange, or other ion exchangemembranes that facilitate the required ion transfer function. Forexample, the circular bubble at the lower right portion of FIG. 4depicts the transfer of an Na+ ion from end chamber 137B-1 to adjacentbase chamber 133B-n through membrane F1, and the circular bubble at thelower left portion of FIG. 4 depicts the transfer of an Na+ ion fromacid chamber 131B-1 into end chamber 137B-2.

Electrolyte solution circulation system 139B may include a reservoir139B-0 and flow lines 139B-1 to 139B-3 that function to circulate anelectrolyte solution 114B through end chambers 137B-1 and 137B-2. Thatis, electrolyte solution 114B can be pumped from reservoir 139B-0 alongfirst flow line 139B-1 to first end chamber 137B-1, from end chamber137B-1 along second flow line 139B-2 to second end chamber 137B-2, andfrom second end chamber 137B-2 along third flow line 139B-3 to reservoir139B-0. In some embodiments (not pictured) it may be desired to separatethe electrolytes so that cathode and anode are two fluid circuits.During operation the electrolyte solution may give up Na+ ions at oneend of ion exchange stack 134B (e.g., as indicated by the Na+ ionpassing from end chamber 137B-1 to base chamber 133B-n in the bubbleview shown in the lower right portion of FIG. 4 ) and reabsorbs Na+ ionsat the opposing end of ion exchange stack 135B (e.g., as indicated bythe Na+ ion passing from acid chamber 132B-1 to end chamber 137B-2 inthe bubble view shown in the lower left portion of FIG. 4 ). In someembodiments, electrolyte solution 114B is implemented using sodiumsulfate or a semi conductive solution such as sodium hydroxide.

In some embodiments, BPED system 110B may be operated in “feed andbleed” operating mode in which portions of both stronger base stream113B-2 and stronger acid stream 112B-2 are diverted (bled) out of thebuffer-tank/electrolyzer flow cycle. That is, as described above, aportion of stronger base stream 113B-2 can be diverted (bled off) andsupplied to the ocean (e.g., by way of valve 146A-3 described above withreference to FIG. 3 ). In addition, as shown in FIG. 4 , a first portion112B-21 of stronger acid stream 112B-2 exiting electrodialysis apparatus130B is returned to the acid buffer tank (not shown), and a secondportion 112B-22 of stronger acid stream 112B-2 is bled off by way of avalve 146B. In some embodiments the bled-off (second) stream portion112B-22 can be processed or otherwise utilized as feedstock forgenerating a commercial product. In one embodiment, BPED system 110Bincludes an electrolyzer 70B that receives and processes acid streamportion 112B-22 to generate hydrogen gas H₂, and a fuel cell 75B thatprocesses the hydrogen gas H₂ to generate supplemental low/zero-carbonelectricity LCE/PS to further enhance the economically sustainability ofa OAE system 100B as a carbon offset system (e.g., by way oftransmitting supplemental electricity LCE/PS to power distributioncircuit 190 (FIG. 1 ) for use by OEA system 100). In some embodiments,one or more additional gasses, such as chlorine gas Cl₂ and/or oxygengas O₂, may be produced (e.g., in addition to or as an alternative tohydrogen gas H₂), and such gases may be sold to further enhance theeconomically sustainability of a OAE system 100B as a carbon offsetsystem. It may be desirable to treat acid stream portion 112B-22 beforeundergoing the electrolyzation process. Some possible methods ofpretreatment, not pictured, may include filtration, chemical,electrochemical, nanofiltration, ultrafiltration, reverse osmosis,heating, and cooling. In other embodiments, not pictured, hydrogen gasfrom reservoir 139B-0 can be fed to fuel cell 75B, or the acid can beutilized in a flow battery to produce supplemental low/zero-carbonelectricity to help offset input power.

FIG. 5 shows a BPED system 110C including a flow control system 140Cthat is modified as described below to facilitate descaling(maintenance) operations during maintenance cycles. In some embodiments,BPED system 110C may be utilized to perform the function ofbase-generating device 110 in OAE system 100 (FIG. 1 ). In otherembodiments BPED system 110C may be utilized in conjunction with otherapplications that benefit from the functions provided by BPED system110C, such as in desalination or water recycling plants. BPED system110C may include fluid buffering system 120A, electrodialysis apparatus130A, modified flow control system 140C and a series of flow lines thatmay be configured and operate in a manner consistent with any of theembodiments described herein. For purposes of brevity, fluid bufferingsystem 120A and electrodialysis apparatus 130A are configured andfunction as described above with reference to FIG. 3 . BPED system 110Cis greatly simplified to emphasize the novel characteristics associatedwith modified flow control system 140C. To this end, the novelcharacteristics of BPED system 110C are generically described withreference to fluid buffering system 120A, electrodialysis apparatus 130Aand associated flow lines that may be configured and operate in a mannerconsistent with any of the embodiments described herein. Additionalfluid flow system features, control circuitry, sensors and other devicesthat may be required to perform the BPED operations can be used.

As indicated in FIG. 5 , normal operations of BPED systems like system110C can produce fouling and scaling S on membranes 135A-1 and 135A-2,and it is sometimes desirable to flush salt chamber 131A and/or basechamber 133A with an acidic fluid to remove the scaling. According tothe present embodiment, modified flow control system 140C may includethree-way valves 146C-11, 146C-12, 146C-21 and 146C-22 that areconfigured to facilitate an acid flush process during maintenanceoperations by way of selectively feeding acid stream 112C-1 from acidbuffer tank 121C-1 to salt chamber 131A and base chamber 133A. In someembodiments, a first valve 146C-11 may be disposed in salt inflow line151C-1 and may communicate with acid inflow line 151C-2 by way of afirst cross-feed line 154C-11, a second valve 146C-12 may be disposed inbase inflow line 151C-3 and may communicate with acid inflow line 151C-2by way of a second cross-feed line 154C-12, a third valve 146C-21 may bedisposed in salt outflow line 152C-1 and may communicate with acidoutflow line 152C-2 by way of a third cross-feed line 154C-21, and afourth valve 146C-22 may be disposed in base outflow line 152C-3 and maycommunicate with acid outflow line 152C-2 by way of a fourth cross-feedline 154C-22. Each three-way valve 146C-11, 146C-12, 146C-21 and 146C-22may be controlled by way of a control signal C generated by the BPEDsystem's control circuit (not shown) to either facilitate normal BPEDsystem operations (as depicted and described with reference to FIG. 6A)or to operate in a maintenance cycle in which valves 146C-11, 146C-12,146C-21 and 146C-22 work in concert to divert portions of acid stream102C-1 from acid buffer tank 121A-2 into one or both of fluid chambers131A and 133A.

FIG. 6A depicts modified BPED system 110C as effectively configured bythe associated control circuit (not shown) during base-generating(normal) operations. During the (first) time periods associated withnormal operations the control circuit (not shown) transmits a firstcontrol signal C1 that deactivates (turns off) valves 146C-11 to146C-22, whereby valves 146C-11 to 146C-22 enter the operating statedepicted in FIG. 6A. Specifically, flow along cross-feed lines 154C-11and 154C-12 can be prevented when valves 146C-11 and 146C-12 are turnedoff, whereby weak acid stream 112C-1 is directed by acid inflow line151C-2 through acid chamber 132A, and strong acid stream 112C-2 isdirected by acid outflow line 152C-2 and acid return line 153C-2 back toacid buffer tank 121C-2. Similarly, when valves 146C-11 and 146C-21 areturned off, salt stream 111C-1 can be directed by salt inflow line151C-1 through salt chamber 131A, and depleted salt stream 111C-2directed by salt outflow line 152C-1 and salt return line 153C-1 back tosalt buffer tank 121C-1. Finally, when valves 146C-12 and 146C-22 areturned off, weak base stream 113C-1 can be directed by base inflow line151C-3 through base chamber 133A, and strong base stream 113C-2 isdirected by base outflow line 152C-3 and base return line 153C-3 back tobase buffer tank 121C-3. Although not shown in FIG. 6A, portions ofstrong acid stream 112C-2 and strong base stream 113C-2 may be bled offduring base-generating operations, as described above with reference toFIGS. 3 and 4 .

FIG. 6B depicts modified BPED system 110C as effectively configuredduring an acid-flush (maintenance cycle) operation. During the (second)time periods associated with acid-flush operations the control circuit(not shown) transmits a second control signal C2 to valves 146C-11 to146C-22. In some embodiments, control signal C2 causes valves 146C-11and 146C-12 to divert the inflow of acid 112C from acid buffer tank121C-2 into salt chamber 131A and base chamber 133A by way of acidinflow line 151C-2 and cross-feed lines 154C-11 and 154C-12, and causesvalves 146C-21 and 146C-22 to divert the outflow of acid 112C from saltchamber 131A and base chamber 132A back to acid buffer tank 132A by wayof cross-feed lines 154C-21 and 154C-22, acid outflow line 152C-2, andacid return line 153C-2. That is, during acid-flush operations thecontrol circuit (not shown) may actuate valves 146C-11 and 146C-12 suchthat at least a portion of acid solution 111C-1 flows from acid buffertank 121C-2 to both salt chamber 131A and base chamber 133A, wherebyaccumulated scaling material disposed in salt chamber 131A and basechamber 133A is dissolved or otherwise removed by contact with the acidsolution. An optional two-way valve 146C-13 may be included in acidinflow line 151C-2 between the junction with cross-feed line 154C-12 andacid chamber 132A and controlled to prevent acid flow through acidchamber 132A to further increase acid flow through salt chamber 131A andbase chamber 133A during acid flush operations. In some embodiments, allfour valves 146C-11 to 146C-22 may be turned on simultaneously (e.g., asindicated in FIG. 6B), and in other embodiments the acid-flush of saltchamber 131A and base chamber 133A may be performed one at a time (e.g.,by activating valves 146C-11 and 146-21 while deactivating valves146C-12 and 146-22, and subsequently deactivating valves 146C-11 and146-21 while activating valves 146C-12 and 146-22). Alternativeembodiments may use motor controlled 3-way valves or 2-way valves withpiping bypass, motorize controlled valves, and metering valves,pneumatically controlled valves, or any combination thereof.

FIGS. 7 to 9 depict BPED systems according to three embodiments in whichthe need for an external fresh water supply is reduced or eliminated bypartially or fully desalinating (pretreating) the available saltfeedstock. When readily available, an external fresh water supply can beused to replace liquid volumes that are bled out of the BPED systemduring the feed-and-bleed operations described above (e.g., outgoingbase stream 113A-21 described above with reference to FIG. 3 and/oroutgoing acid stream 112B-21 described above with reference to FIG. 4 ).Replacing the lost liquid volume with fresh water (when available) mayprovide the benefit of maintaining the purity of the outgoing base andacid product. However, to maximize ocean deacidification whileminimizing danger to sea life it may become necessary to deploy multipleOAE systems at corresponding locations around the periphery of or onislands disposed in each ocean (i.e., to produce uniform diffusion ofbase material to the ocean's seawater). To achieve uniform diffusion, itmay become necessary to deploy some of the OEA systems in remotelocations where a reliable fresh water supply may be unavailable. TheBPED systems described below with reference to FIGS. 7 to 9 can bemodified to include a pretreatment unit that reduces or eliminates ahost OAE system's dependence on a fresh water supply by at leastpartially desalinating an externally supplied feedstock solution andthen utilizing the reduced-salt fluid to replace bled off acid and/orbase solution (i.e., in place of processed or fresh water from anexternal source). Note that FIGS. 7 to 9 are greatly simplified and thatadditional BPED system features are omitted for brevity and clarity. Forexample, for reasons like those mentioned above with reference to BPEDsystem 110C (FIGS. 5, 6A and 6B), each of the BPED systems depicted inFIGS. 7 to 9 is described with reference to generalized electrodialysisapparatus 130A. In addition, the flow control systems of each of theBPED systems depicted in FIGS. 7 to 9 is understood to include thedepicted valves and pumps, even if the depicted valves/pumps are notspecifically referenced as part of the associated flow control system inthe description below. Finally, the flow control systems of each of thedepicted BPED systems may be modified to include certain flow controlfeatures discussed above (e.g., the valves and cross-feed linesdescribed above with reference to FIGS. 5, 6A and 6B).

FIG. 7 depicts a modified BPED system 110D including a reverse osmosisunit 160D that is used to process (pretreat) seawater 50D (saltfeedstock). BPED system 110D can also include a fluid buffering system120D and a flow control system 140D that are configured as describedbelow to transmit salt, acid and base streams through an electrodialysisapparatus 130A to facilitate base-generation and acid generationoperations similar to those described above.

Referring to the upper portion of FIG. 7 , reverse osmosis unit 160D canbe operably coupled between an optional settling tank (salt feedstocksource) 60D and fluid buffering system 120D. Reverse osmosis unit 160Dmay process seawater 50D using known techniques and is depicted anddescribed below in a greatly simplified form for brevity. In general,reverse osmosis unit 160D may utilize a filter 165D to separate salt andother minerals from seawater 50D, thereby generating a permeate(reduced-salt fluid) 115D and a concentrate (high-salt fluid) 111D-0.

Fluid buffering system 120D and flow control system 140D can beconfigured to receive and store concentrate 111D-0 and permeate 115D tofacilitate base-generation and acid generation operations similar tothose described above. Fluid buffering system 120D may include buffertanks 121D-1, 121D-2 and 121D-3 that respectively store salt, acid andbase solutions in the manner described above with reference to FIGS. 3and 5 . In general, flow control system 140D can be configured to directconcentrate 111D-0 to salt tank 121D-1, and to direct permeate 115D to121D-2 and 121D-3. In one embodiment, concentrate 111D-0 is directlytransmitted from reverse osmosis unit 160D to salt buffer tank 121D-1 byway of a first feed line 155D-10, and permeate 115D is directed fromreverse osmosis unit 160D to acid buffer tank 121D-2 and base buffertank 121D-3 by way of a second feed line 155D-20. In some embodimentsfluid buffering system 120D includes one or more additional buffer tanksthat may be utilized to facilitate the distribution of permeate 115D toacid buffer tank 121D-2 and base buffer tank 121D-3. In the specificembodiment depicted in FIG. 7 , a first additional buffer tank 121D-4receives permeate 115D from reverse osmosis unit 160D, and distributesportions of permeate 115D to a second buffer tank 121D-5 and a thirdbuffer tank 121D-6 by way of intermediate lines 155D-21 and 155D-22,respectively, and then the distributed portions of permeate 115D aredirected to acid buffer tank 121D-2 and base buffer tank 121D-3 by wayof feed lines 155D-31 and 155D-32, respectively. In other embodiments asmaller or larger number of additional buffer tanks may be used orpermeate 115D may be directly passed from reverse osmosis unit 160D toacid buffer tank 121D-2 and base buffer tank 121D-3. In each of thesecases, salt-free water (permeate) 115D is directed to both acid buffertank 121D-2 and base buffer tank 121D-3, and high-salt fluid(concentrate) 111D-0 is supplied to salt tank 121D-1.

Referring to the lower portion of FIG. 7 , in some embodiments flowcontrol system 140D is further configured to facilitate feed-and-bleedbase-generating and acid-generating operations similar to thosedescribed above with reference to FIG. 5 (i.e., such that a portion ofstrong acid stream 112D-2 leaving acid chamber 132A can be diverted toprovide acid substance 112D-OUT, and a portion 113D-22 of strong basestream 113D-2 leaving base chamber 133A is diverted to provide basesubstance 113D-OUT). In addition, flow control system 140D can befurther modified to include an additional three-way valve 146D thatsplits depleted salt stream 111D-2 leaving salt chamber 131A on saltoutflow line 152D-1 into two portions, whereby a first portion 111D-21is returned to salt buffer tank 121D-1, and a second portion 111D-22 canbe combined (mixed) with diverted base stream portion 113D-22 to formbase substance 113D-OUT.

FIG. 8 depicts a modified BPED system 110E including a chemical acidconcentrator unit 160E that is used to process (pretreat) brine 66E(salt feedstock) and a portion 112E-22 of strong acid stream 112E-2 inorder to generate both a reduced-salt fluid 111E-0 (i.e., having a saltconcentration lower than that of brine 66E) and a high-concentrationacid 112E-OUT. BPED system 110E may also include a fluid bufferingsystem 120E and a flow control system 140E that are configured asdescribed below to transmit reduced-salt fluid 111E-0 to all three of asalt buffer tank 121E-1, an acid buffer tank 121E-2 and a base buffertank 121E-3, and to direct salt, acid and base streams through anelectrodialysis apparatus 130A to facilitate base-generation and acidgeneration operations similar to those described above.

Referring to the upper portion of FIG. 8 , chemical acid concentratorunit 160E is operably coupled between an optional brine feed tank (saltfeedstock source) 60E and fluid buffering system 120E. In oneembodiment, chemical acid concentrator unit 160E is configured toprocess brine 66E and a portion of the acid stream 112E-2 using anosmotically-driven forward osmosis process in a manner that generatesboth reduced-salt fluid 111E-0 and a high-concentration acid 112E-OUT.Osmotically-driven forward osmosis processes are known in the art (see,for example, “Osmotic concentration of succinic acid by forward osmosis:Influence of feed solution pH and evaluation of seawater as drawsolution”, Jeng Yih Law et al. Chinese Journal of Chemical Engineering,Volume 26, Issue 5, May 2018, Pages 976-983), and those skilled in theart are capable of generating chemical acid concentrator unit 160E suchthat it implements the osmotically-driven forward osmosis processdepicted in FIG. 8 .

Fluid buffering system 120E and flow control system 140E can beconfigured to receive and store reduced-salt fluid 111E-0 and tofacilitate base-generation and acid generation operations similar tothose described above. Fluid buffering system 120E may include buffertanks 121E-1, 121E-2 and 121E-3 that respectively store salt, acid andbase solutions in the manner described above with reference to FIG. 7 .In this embodiment, flow control system 140E can be configured to directreduced-salt fluid 111E-0 to salt buffer tank 121E-1, and to direct afirst portion 111E-11 of a salt stream 111E-1 exiting salt buffer tank121E-1 to salt chamber 131A, and to direct a second portion 111E-12 ofsalt stream 111E-1 to acid buffer tank 121E-2 and base buffer tank121E-3. In some embodiments, fluid buffering system 120E includes one ormore intermediate buffer tanks that may be utilized to facilitate thedistribution of salt stream portion 111E-12 to acid buffer tank 121E-2and base buffer tank 121E-3. In the specific embodiment depicted in FIG.8 , a first intermediate buffer tank 121E-4 receives salt stream portion111E-12 from salt buffer tank 121E-1, and distributes a firstsub-portion 111E-121 of salt stream portion 111E-12 to a secondintermediate buffer tank 121E-5 and a second sub-portion 111E-122 ofsalt stream portion 111E-12 to a third intermediate buffer tank 121E-6by way of corresponding intermediate lines, and then the distributedsub-portions are directed from intermediate buffer tanks 121E-5 and121E-6 to acid buffer tank 121E-2 and base buffer tank 121E-3,respectively, by way of corresponding feed lines. In other embodiments asmaller or larger number of intermediate buffer tanks may be used. Ineach of these cases, reduced-salt fluid can be directed to all three ofsalt buffer tank 121E-1, acid buffer tank 121E-2 and base buffer tank121E-3.

Referring to the lower portion of FIG. 8 , in some embodiments flowcontrol system 140E is further configured to facilitate a feed-and-bleedoperations similar to those described above with reference to FIG. 7(e.g., such that a portion of strong base stream 113E-2 leaving basechamber 133A is diverted and mixed with a portion of depleted saltstream 111E-2 leaving salt chamber 131E to provide base substance113E-OUT). In this embodiment, flow control system 140E includes athree-way valve 146E that splits strong acid stream 112E-2 leaving acidchamber 132E into a first portion 112E-21 that is returned to acidbuffer tank 121E-2 and a second portion 112E-22 that is fed to chemicalacid concentrator unit 160E, for example, by way of a fourthintermediate buffer tank 121E-7.

FIG. 9 depicts a modified BPED system 110F according to anotherembodiment in which a chemical acid concentrator (pretreatment) unit160F receives brine 66F from a brine feed tank (salt feedstock source)60F and a strong acid stream portion 112F-22 from an acid concentrationfeed tank 121F-7 and generates saltwater (reduced-salt fluid) 111F-0 anda concentrated acid solution 112F-OUT in a manner similar to thatdescribed above with reference to FIG. 8 . In addition, reduced-saltfluid 111F-0 can be supplied from concentrator unit 160F to salt (first)buffer tank 121F-1, a stream portion 111F-11 leaving salt buffer tank121F-1 is directed to salt chamber 131A of electrodialysis apparatus130A, and a stream portion 111F-12 leaving salt buffer tank 121F-1 issupplied to base (third) buffer tank 121F-3 by way of optionalintermediate buffer tank 121F-6. In the same manner as that associatedwith the embodiment shown in FIG. 8 , electrodialysis apparatus 130A mayfunction to generate a depleted salt stream 111F-2 and a concentratedbase stream 113F-2 that are directed along associated output and returnlines to generate base substance 113F-OUT, and to generate a strong acidstream 112F-2 that is split to two streams 112F-21 and 112F-22respectively directed to acid buffer tank 121F-1 and acid concentrationfeed tank 121F-7.

BPED system 110F differs from BPED 110E (FIG. 8 ) in that deionizedwater 77F generated by a deionized water source 70F is supplied to acidbuffer tank 121F-2. Deionized water source 70F can be integrated (i.e.,part of BPED system 110F), or it may be implemented as an external unit.Deionized water 77F may be supplied by way of one or more intermediatebuffer tanks (e.g., by way of buffer tanks 121F-4 and 121F-5, asdepicted in FIG. 9 ), or may be supplied directly from deionized watersource 70F to acid buffer tank 121F-2. Note that deionized water 77F isnot supplied to base buffer tank 121F-3. That is, deionized water 77Fcan be utilized solely to replenish the bled-off (diverted) volumeassociated with strong acid stream portion 112F-22, which is used togenerate concentrated acid substance 112F-OUT. The use of deionizedwater 77F may produce strong acid stream 112F-2 with a substantiallylower salt content than corresponding stream 112E-2 described above withreference to FIG. 8 , thereby facilitating the generation of clean(substantially salt-free) concentrated acid solution 112F-OUT. Althoughthe generation and use of deionized water 77F may arguably makes BPEDsystem 110F somewhat more expensive to operate (i.e., in comparison toBPED system 110E), this arrangement may be preferred in applicationswhere the purity of concentrated acid solution 112F-OUT is valued higherthan the cost of generating deionized water 77F.

FIG. 10 depicts alkalinity product generation unit 147A (FIG. 3 ) thatfunctions to generate ocean alkalinity product 113A-OUT according to asimplified embodiment. As mentioned above, to avoid endangering sealife, and to maximize the potential benefits to sea life, oceanalkalinity product 113A-OUT can be a well characterized solutionincluding a mixture of the base substance and saltwater that is released(supplied to the ocean) only after verifying that the base substance isfully dissolved in the solution, and that the mixture has an appropriatepH value. To this end, alkalinity product generation unit 147A canfunction to both verify and, if necessary, perform post-processing ofthe base solution generated by base generating device 110A (FIG. 3 )before releasing the verified/processed base solution as oceanalkalinity product 113A-OUT. In the embodiment shown in FIG. 10 ,alkalinity product generation unit 147A may utilize two buffer tanks148A and 149A to verify/process base solution. Note that theverification and optional processing described below is not limited tothe depicted two-buffer-tank arrangement and may be achieved using asingle buffer tank or more than two buffer tanks. That is, theembodiment is intended to illustrate various options and not intended tobe limiting.

Referring to the upper portion of FIG. 10 , buffer tank 148A can beconfigured to store base solution 113A-3 that is supplied in sub-stream113A-22 by way of valve 146A-3 (see FIG. 3 ). At least one sensor S4 canbe operably disposed in buffer tank 148A and may be configured tomeasure pH and optional additional characteristics of base solution113A-3. In one embodiment, the additional characteristics may includedata verifying that the base substance is fully dissolved in basesolution 113A-3. Base solution data 182A-1 generated by sensor S4 can betransmitted to controller 180 (FIG. 1 ). In some embodiments, when basesolution data 182A-1 indicates base solution 113A-3 has an undesirablepH or other undesirable characteristic, controller 180 may initiateprocessing of base solution 113A-3 to correct the undesirablecharacteristic. For example, controller 180 may adjust the pH of basesolution 113A-3 by retaining base solution 113A-3 in buffer tank 148Afor an extended period to facilitate a reaction with air or CO₂ (i.e.,partially equilibrate/pull down CO₂ into the base solution while inbuffer tank 148A). In other cases, controller 180 may generate one ormore control signals (not indicated) to initiate one or more processes(e.g., low-energy stirring and/or venting processes, or diluting withfresh seawater or depleted brine) to correct corresponding undesirablecharacteristics.

Buffer tank 149A can be configured to receive and store a base/saltsolution 113A-4, which comprises a mixture of base solution stream113A-23 from buffer tank 148A and a dilution stream from another source.This arrangement can be utilized, for example, when the pH of basesolution 113A-3 is too high for release into the ocean, and involvesutilizing the dilution stream to adjust the pH of base solution 113A-3and/or by reacting base solution 113A-4 with air or CO₂ to achieve anacceptable pH value. In the depicted embodiment, the dilution streamcomprises processed feedstock (depleted salt) solution provided in saltsub-stream 111A-22 received from valve 146A-1 (see FIG. 3 ). In otherembodiments (not shown), the saltwater stream may comprise seawater orbrine. In yet other cases, where base solution 113A-3 already includes asufficient amount of salt, the dilution stream may comprise fresh ordeionized water. In any case, when base solution data 182A-1 indicatesthat the pH and optional other characteristics of base solution 113A-3are within acceptable ranges, controller 180 may activate control signal185A-1 that controls valve 146A-4, whereby base solution 113A-3 can bemixed with an appropriate quantity of diluting liquid. At least onesensor S5 may be operably disposed in buffer tank 149A and is configuredto measure pH and optional additional characteristics of base/saltsolution 113A-4. Alkaline product data 182A-2 generated by sensor S5 canbe transmitted to controller 180 (FIG. 1 ), and controller 180 mayadjust the flow rate of dilution fluid through valve 146A-4 to fine tunethe pH value of base/salt solution 113A-4 in buffer tank 149A. Only whenalkaline product data 182A-2 verifies the acceptability of the pH value(and optional other characteristics) of base/salt solution 113A-4,controller 180 may control the flow of base/salt solution 113A-4 frombuffer tank 149A (e.g., by way of controlling an outflow valve 146A-5 byway of control signal 185A-2), thereby supplying ocean alkalinityproduct 113A-OUT to the ocean (e.g., by way of pump 145A-33, shown inFIG. 3 ).

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. It is not intendedthat the invention be limited by the specific examples provided withinthe specification. While the invention has been described with referenceto the aforementioned specification, the descriptions and illustrationsof the embodiments herein are not meant to be construed in a limitingsense. Numerous variations, changes, and substitutions will now occur tothose skilled in the art without departing from the invention.Furthermore, it shall be understood that all aspects of the inventionare not limited to the specific depictions, configurations or relativeproportions set forth herein which depend upon a variety of conditionsand variables. It should be understood that various alternatives to theembodiments of the invention described herein may be employed inpracticing the invention. It is therefore contemplated that theinvention shall also cover any such alternatives, modifications,variations or equivalents. It is intended that the following claimsdefine the scope of the invention and that methods and structures withinthe scope of these claims and their equivalents be covered thereby.

1. An electrochemical ocean alkalinity enhancement (OAE) systemconfigured to capture atmospheric carbon dioxide and mitigate oceanacidification, the OAE system comprising: a base-generating device thatis configured to generate an ocean alkalinity product by processing afeedstock solution and configured to supply the ocean alkalinity productto an ocean at a designated outfall location, wherein the oceanalkalinity product includes a salt solution comprising a dissolved basesubstance; and a control circuit configured to control operationsperformed by the base-generating device such that the ocean alkalinityproduct is supplied to the ocean only when input data received by thecontrol circuit indicates (1) sufficient low/zero-carbon electricity isavailable to operably power the base-generating device, (2) thebase-generating device is operably configured to safely generate andsupply the ocean alkalinity product, and (3) supplying the oceanalkalinity product will not endanger sea life in the ocean.
 2. The OAEsystem of claim 1, wherein the base-generating device comprises abipolar electrodialysis (BPED) system comprising: a buffering systemcomprising a first buffer tank configured to store the feedstocksolution, a second buffer tank configured to store an acid solution, anda third buffer tank configured to store a base solution; anelectrodialysis apparatus comprising at least one salt chamber, at leastone acid chamber and at least one base chamber; and a flow controlsystem configured to: (i) direct a first stream comprising a portion ofthe feedstock solution from the first buffer tank through the at leastone salt chamber, (ii) direct a second stream comprising at least aportion of the acid solution from the second buffer tank through the atleast one acid chamber, and (iii) direct a third stream comprising aportion of the base solution from the third buffer tank through the atleast one base chamber, wherein the electrodialysis apparatus isconfigured to generate both a strong base stream including the fullydissolved base substance and a strong acid stream containing an acidsubstance by electrochemically processing the first stream, the secondstream and the third stream.
 3. The OAE system of claim 2, wherein theelectrodialysis apparatus comprises: a plurality of salt chambers, aplurality of acid chambers and a plurality of base chambers arranged inseries such that each the salt chamber is disposed between an adjacentthe acid chamber and an adjacent the base chamber, and each the basechamber is disposed between an adjacent the salt chamber and an adjacentthe acid chamber; a plurality of first membranes respectively disposedbetween each the salt chamber and the adjacent acid chamber, each of thefirst membranes being configured to pass chlorine ions from the adjacentsalt chamber to the adjacent acid chamber; a plurality of secondmembranes respectively disposed between each the salt chamber and theadjacent base chamber, each of the second membranes being configured topass sodium ions from the adjacent salt chamber to the adjacent basechamber; and a plurality of third membranes respectively disposedbetween each the acid chamber and the adjacent base chamber, each of thethird membranes being configured to: (i) pass hydrogen ions from theadjacent base chamber to the adjacent acid chamber, and (ii) to passhydroxide ions from the adjacent acid chamber to the adjacent basechamber.
 4. The OAE system of claim 2, wherein the BPED system furthercomprises an electrolyzer configured to generate hydrogen gas byprocessing the acid substance.
 5. The OAE system of claim 4, wherein theBPED system further comprises a fuel cell configured to generatesupplemental low/zero-carbon electricity by processing the hydrogen gas.6. The OAE system of claim 2, wherein the control circuit is furtherconfigured to control the flow control system such that: during a firsttime period a portion of the feedstock solution flows from the firstbuffer tank through the at least one salt chamber and a portion of thebase solution flows from the third buffer tank through the at least onebase chamber, and during a second time period, at least a portion of theacid solution flows from the second buffer tank through at least one ofthe salt chamber and the base chamber.
 7. The OAE system of claim 2,wherein the flow control system comprises: a first three-way valveconnected to a salt inflow line between the first buffer tank and the atleast one salt chamber and operably coupled to an acid inflow line by afirst cross-feed line, wherein the acid inflow line is configured totransmit the second stream from the second buffer tank to the at leastone acid chamber, a second three-way valve connected to a base inflowline between the third buffer tank and the at least one base chamber andoperably coupled to the acid inflow line by a second cross-feed line,and wherein the control circuit is further configured to control thefirst three-way valve and the second three-way valve such that: during afirst time period a portion of the feedstock solution flows from thefirst buffer tank through the first three-way valve to the at least onesalt chamber and a portion of the base solution flows from the thirdbuffer tank through the second three-way valve to the at least one basechamber, and during a second time period, at least a portion of the acidsolution flows from the second buffer tank through the first and secondthree-way valves to at least one of the salt chamber and the basechamber.
 8. The OAE system of claim 2, wherein the BPED system furthercomprises a pretreatment unit configured to generate a reduced-saltfluid by processing the feedstock solution, and wherein the flow controlsystem is further configured to direct the reduced-salt fluid to atleast one of the second buffer tank and the third buffer tank.
 9. TheOAE system of claim 8, wherein the feedstock solution comprisesseawater, wherein the pretreatment unit comprises a reverse osmosis unitconfigured to process the seawater and to generate both the reduced-saltfluid and a high-salt fluid, the high-salt fluid having a higher saltconcentration than both the seawater and the reduced-salt fluid, andwherein the flow control system is further configured to direct thehigh-salt fluid to the first buffer tank and to direct the reduced-saltfluid to both the second buffer tank and the third buffer tank.
 10. TheOAE system of claim 8, wherein the feedstock solution comprises brine,wherein the pretreatment unit comprises a chemical acid concentratorconfigured to process the brine and at least a portion of the acidsubstance to generate a concentrated acid substance and the reduced-saltfluid, wherein the reduced-salt fluid has a lower salt concentrationthan the brine, and wherein the flow control system is furtherconfigured to direct the reduced-salt fluid to the first buffer tank.11. The OAE system of claim 10, wherein the flow control system isfurther configured to direct portions of the reduced-salt fluid to boththe second buffer tank and the third buffer tank.
 12. The OAE system ofclaim 10, wherein the BPED system further comprises a water deionizationunit configured to generate deionized water, and wherein the flowcontrol system is further configured to direct the deionized water tothe second buffer tank and to direct a portion of the reduced-salt fluidto the third buffer tank.
 13. An electrochemical ocean alkalinityenhancement (OAE) system comprising: a BPED system comprising: abuffering system comprising an acid buffer tank configured to store anacid solution, an electrodialysis apparatus comprising at least one saltchamber, at least one acid chamber, at least one base chamber, and aflow control system comprising a plurality of flow lines connectedbetween the buffering system and the electrodialysis apparatus; and acontrol circuit configured to control the flow control system and theelectrodialysis apparatus such that: during a base generating operation,the flow control system directs a salt stream through the at least onesalt chamber, directs an acid stream comprising at least a portion ofthe acid solution from the acid buffer tank through the at least oneacid chamber, and directs a base stream through the at least one basechamber, and such that the electrodialysis apparatus electrochemicallyprocesses the salt stream passing through the at least one salt chamberin a way that increases an amount of acid in the acid stream and anamount of base substance in the base stream; and during a descalingmaintenance operation, the flow control system directs the acid streamfrom the acid buffer tank through the at least one salt chamber and theat least one base chamber.
 14. The OAE system of claim 13, wherein theelectrodialysis apparatus further comprises a first ion-permeablemembrane disposed between the at least one salt chamber and the at leastone acid chamber, and a second ion-permeable membrane disposed betweenthe at least one salt chamber and the at least one base chamber; whereinelectrochemically processing the salt stream during the base generatingoperation produces scaling material on the first ion-permeable membraneand the second ion-permeable membrane; and wherein the control circuitis further configured to direct the acid stream through the at least onesalt chamber and the at least one base chamber during the descalingmaintenance operation until the scaling material is removed from thefirst ion-permeable membrane and second ion-permeable membrane.
 15. TheOAE system of claim 13, wherein the buffering system further comprises asalt buffer tank configured to store a feedstock solution and a basebuffer tank configured to store a base solution; wherein the pluralityof flow lines) comprises a salt inflow line extending from an outflowport of the salt buffer tank to the electrodialysis apparatus, an acidinflow line extending from an outflow port of the acid buffer tank tothe electrodialysis apparatus, and a base inflow line extending from anoutflow port of the base buffer tank to the electrodialysis apparatus;and wherein, during the base generating operation, the control circuitcontrols the flow control system such that the salt stream comprises aportion of the feedstock solution that is directed by the salt inflowline through the at least one salt chamber, the acid stream comprises aportion of the acid solution that is directed by the acid inflow linethrough the at least one acid chamber, and the base stream comprises aportion of the base solution that is directed by the base inflow linethrough the at least one base chamber.
 16. The OAE system of claim 15,wherein the plurality of flow lines further comprises a first cross-feedline disposed between the acid inflow line the salt inflow line and asecond cross-feed line disposed between the acid inflow line the baseinflow line; wherein the flow control system further comprises aplurality of valves; and wherein the control circuit is configured tocontrol the plurality of valves such that, during the descalingmaintenance operation, a first portion of the acid stream is directedalong the first cross-feed line and through the at least one saltchamber, and a second portion of the acid stream is directed along thesecond cross-feed line and through the at least one base chamber. 17.The OAE system of claim 16, wherein the plurality of valves comprises: afirst three-way valve connected to the salt inflow line between the saltbuffer tank and the at least one salt chamber and operably coupled tothe acid inflow line by the first cross-feed line, and a secondthree-way valve connected to the base inflow line between the basebuffer tank and the at least one base chamber and operably coupled tothe acid inflow line by the second cross-feed line; and wherein thecontrol circuit is further configured to control the first three-wayvalve and the second three-way valve such that: during saidbase-generating operation, the feedstock solution flows from the saltbuffer tank through the first three-way valve to the at least one saltchamber and the base solution flows from the base buffer tank throughthe second three-way valve to the at least one base chamber, and duringeach descaling, at least a portion of the acid solution flows from theacid buffer tank through the first and second three-way valves to boththe at least one salt chamber and the base chamber.
 18. The OAE systemof claim 16, wherein the plurality of flow lines further comprises: atleast one salt outflow line extending from the electrodialysis apparatusto an inflow port of the salt buffer tank, at least one acid outflowline extending from the electrodialysis apparatus to an inflow port ofthe acid buffer tank, at least one base outflow line extending from theelectrodialysis apparatus to an inflow port of the base buffer tank, athird cross-feed line disposed between the at least one salt outflowline and the at least one acid outflow line, a fourth cross-feed linedisposed between the at least one base outflow line and the at least oneacid outflow line; and wherein the control circuit is further configuredto control the plurality of valves such that, during the descalingmaintenance operation, said first portion of the acid stream exiting theat least one salt chamber is directed along the third cross-feed line tothe at least one acid outflow line, and the second portion of the acidstream exiting the at least one base chamber is directed along thefourth cross-feed line to the at least one acid outflow line.
 19. Anelectrochemical ocean alkalinity enhancement (OAE) system comprising: aBPED system comprising: a buffering system comprising a salt buffer tankconfigured to store the feedstock solution, an acid buffer tankconfigured to store an acid solution, and a base buffer tank configuredto store a base solution, an electrodialysis apparatus comprising atleast one salt chamber, at least one acid chamber, at least one basechamber, at least one first ion-permeable membrane disposed between thesalt chamber and the acid chamber, a second ion-permeable membranedisposed between the salt chamber and the base chamber, and a flowcontrol system comprising a plurality of flow lines connected betweenthe buffering system and the electrodialysis apparatus; and a controlcircuit configured to control the flow control system and theelectrodialysis apparatus such that: during a base generating operation,the flow control system directs a salt stream comprising a portion ofthe feedstock solution from the salt buffer tank through the at leastone salt chamber, directs an acid stream comprising at least a portionof the acid solution from the acid buffer tank through the at least oneacid chamber, and directs a base stream comprising a portion of the basesolution from the base buffer tank through the at least one basechamber, and such that the electrodialysis apparatus electrochemicallyprocesses the salt stream passing through the at least one salt chamberin a way that increases an amount of acid in the acid stream and theamount of base substance in the base stream, whereby scaling material isproduced on the first ion-permeable membrane and the secondion-permeable membrane; and during a descaling maintenance operation,the flow control system directs the acid stream from the acid buffertank through the at least one salt chamber and the at least one basechamber until the scaling material is removed from the firstion-permeable membrane and second ion-permeable membrane.
 20. Anelectrochemical ocean alkalinity enhancement (OAE) system configured tocapture atmospheric carbon dioxide and mitigate ocean acidification, theOAE system including a bipolar electrodialysis (BPED) system that iscontrolled by a control circuit to perform base-generating operationsduring first time periods and maintenance operations during second timeperiods, the BPED system being configured to generate an oceanalkalinity product including a salt solution and a dissolved basesubstance by electrochemically processing a feedstock solution whenperforming the base-generating operations, wherein the BPED systemcomprises: a buffering system comprising a first buffer tank configuredto store the feedstock solution, a second buffer tank configured tostore an acid solution, and a third buffer tank configured to store abase solution; an electrodialysis apparatus comprising at least one saltchamber, at least one acid chamber and at least one base chamber; and aflow control system configured to: (i) direct a first stream comprisinga portion of the feedstock solution from the first buffer tank throughthe at least one salt chamber, (ii) direct a second stream comprising atleast a portion of the acid solution from the second buffer tank throughthe at least one acid chamber, and (iii) direct a third streamcomprising a portion of the base solution from the third buffer tankthrough the at least one base chamber, wherein the electrodialysisapparatus is configured to generate both an acid substance and at leasta portion of the ocean alkalinity product by electrochemicallyprocessing the first stream, the second stream and the third stream, andwherein the flow control system comprises: a first three-way valveconnected to a salt inflow line between the first buffer tank and the atleast one salt chamber and operably coupled to an acid inflow line by afirst cross-feed line, wherein the acid inflow line is configured totransmit the second stream from the second buffer tank to the at leastone acid chamber, and a second three-way valve connected to a baseinflow line between the third buffer tank and the at least one basechamber and operably coupled to the acid inflow line by a secondcross-feed line, and wherein the control circuit is further configuredto control the first three-way valve and the second three-way valve suchthat: during each said first time period the feedstock solution flowsfrom the first buffer tank through the first three-way valve to the atleast one salt chamber and the base solution flows from the third buffertank through the second three-way valve to the at least one basechamber, and during each said second time period, at least a portion ofthe acid solution flows from the second buffer tank through the firstand second three-way valves to both the at least one salt chamber andthe base chamber.